Communications of Staphylococcus aureus and non-aureus Staphylococcus species from bovine intramammary infections and teat apex colonization

Abstract

The role of non-aureus staphylococci (NAS) in the risk of acquisition of intramammary infections with Staphylococcus aureus is vague and still under debate. The objectives of this study were to (1) investigate the distribution patterns of NAS species from milk and teat skin in dairy herds with automatic milking systems, and (2) examine if the isolated NAS influences the expression of S. aureus virulence factors controlled by the accessory gene regulator (agr) quorum sensing system. In 8 herds, 14 to 20 cows with elevated somatic cell count were randomly selected for teat skin swabbing and aseptic quarter foremilk samples from right hind and left front quarters. Teat skin swabs were collected using the modified wet-dry method and milk samples were taken aseptically for bacterial culture. Colonies from quarters with suspicion of having NAS in milk or teat skin samples (or both) were subjected to MALDI-TOF assay for species identification. To investigate the interaction between S. aureus and NAS, 81 isolates NAS were subjected to a qualitative β-galactosidase reporter plate assay. In total, 373 NAS isolates were identified representing 105 from milk and 268 from teat skin of 284 quarters (= 142 cows). Sixteen different NAS species were identified, 15 species from teat skin and 10 species from milk. The most prevalent NAS species identified from milk were Staphylococcus epidermidis (50%), Staphylococcus haemolyticus (15%), and Staphylococcus chromogenes (11%), accounting for 76%. Meanwhile, the most prevalent NAS species from teat skin were Staphylococcus equorum (43%), S. haemolyticus (16%), and Staphylococcus cohnii (14%), accounting for 73%. Using reporter gene fusions monitoring transcriptional activity of key virulence factors and regulators, we found that out of 81 supernatants of NAS isolates, 77% reduced expression of hla, encoding a-hemolysin, 70% reduced expression of RNAIII, the key effector molecule of agr, and 61% reduced expression of spa encoding protein A of S. aureus, respectively. Our NAS isolates showed 3 main patterns: (1) downregulation effect such as S. chromogenes (milk) and Staphylococcus xylosus (milk and teat), (2) no effect such as Staphylococcus sciuri (teat) and S. vitulinus (teat), and the third pattern (c) variable effect such as S. epidermidis (milk and teat) and S. equorum (milk and teat). The pattern of cross-talk between NAS species and S. aureus virulence genes varied according to the involved NAS species, habitat type, and herd factors. The knowledge of how NAS influences S. aureus virulence factor expression could explain the varying protective effect of NAS on S. aureus intramammary infections.

Non-aureus Staphylococci Species in the Teat Canal and Milk in Four Commercial Swiss Dairy Herds

“…Although the relationship between NAS species causing IMI and those colonizing the teat canal has rarely been quantified (17), a difference in distribution of NAS species between teat canal samples and milk samples was expected. Previous studies found uneven distributions of different NAS species in milk samples and teat apices, including NAS species relevant and less relevant for IMI respectively (8, 16, 27, 31). The teat canal acts as a barrier against invading microorganisms causing IMI and several studies have shown that it harbors several different bacterial species, including Staphylococcus spp., Enterobacteriaceae, Streptococcus spp ., and Clostridium spp .…”

The Milk Microbiota of the Spanish Churra Sheep Breed: New Insights into the Complexity of the Milk Microbiome of Dairy Species

“…However, different Staphylococcus spp. appear to have different roles in relation to the development of this kind of infections [ 28 ]. In this study, we might relate the high abundance in Staphylococcus in Churra milk samples with the reported low microbial diversity value.…”

Typeability of MALDI-TOF assay for identification of non-aureus staphylococci associated with bovine intramammary infections and teat apex colonization

“…About 30 to 40 lactating dairy cows were selected randomly from each herd on the basis of the criteria of having no clinical mastitis, SCC ≥200,000 cells/mL at the preceding milk recording, and not subjected to antibiotic therapy during the 4 wk before sample collection. From each cow with an odd laboratory running number, teat skin swab and aseptic milk samples were taken from right hind and left front quarters (Mahmmod et al, 2018).…”